RIGONCI: Refugees from Asian wars crossed into Slovenia from Croatia on Wednesday as border closures elsewhere forced them to find new routes to rich European countries and concern grew over the plight of those stranded in wet, freezing weather.

On the Croatian-Serbian border, thousands of migrants spent the night camped out at the Berkasovo-Bapska crossing after Croatia closed the gates.

And in an indication that refugees and migrants were still desperate to reach Europe before winter weather made sea crossings too perilous, two boatloads landed at a British military base on Cyprus - the first such arrivals on the island.

With many now trapped in deteriorating conditions in the Balkans, European Commission President Jean-Claude Juncker called an extraordinary meeting of several European leaders to take place on Sunday.

Juncker invited the leaders of Austria, Bulgaria, Croatia, the former Yugoslav Republic of Macedonia, Germany, Greece, Hungary, Romania, Serbia and Slovenia.

"In view of the unfolding emergency in the countries along the Western Balkans migratory route, there is a need for much greater cooperation, more extensive consultation and immediate operational action," the commission said in a statement.

Europe's biggest refugee and migrant crisis since World War II has seen hundreds of thousands of people fleeing war and poverty in the Middle East, Asia and Africa this year, with hundreds losing their lives in risky voyages across the Mediterranean.

Hungary sealed its border with Croatia last week, blocking entry with a steel fence and razor wire. Croatia began directing migrants west to Slovenia, which has tried to stem the flow as people looked for new routes and bottlenecks built up through the Balkans.

Both Slovenia and Hungary are part of Europe's passport-free Schengen Area while Croatia is not. Most want to continue their journey on to Austria and Germany, the most popular destination.

Hazem Al Mousa, a 30-year-old Syrian from Aleppo, crossed into Slovenia on Wednesday near the town of Rigonci with his three sisters, brother and 84-year-old grandmother in a wheelchair.

"It is most important that my grandmother gets medical assistance and my sisters go to school and I'll try to find some work," he said. "I am so afraid that Germany will close its borders. I hope we will make it. We keep fighting and let's hope for a miracle."

Travelling with him was Homayoon Hoseini, 16, from Afghanistan, whose parents were killed by the Taliban.

"Some friends in Iran helped me pay for this trip. I want to go Amsterdam and find a school there." he said.

He had spent the night under open skies at the Croatian-Slovenian border.

"It was so cold. We were trying to keep ourselves warm and lit fires but that didn't help. Thank God for the sun today," he said.

SLOVENIA SEEKS HELP

Slovenia's parliament passed legislation on Wednesday to give the army more power to help police guarding the border, and Prime Minister Miro Cerar said he would ask the European Union for police reinforcements and financial help

More than 20,000 migrants have arrived in Slovenia since Saturday morning in order to pass through to Austria.

On the Croatian-Serbian border, about 3,500 migrants spent the night in freezing cold at the Berkasovo-Bapska crossing, huddling in tents or under tarpaulins provided by aid groups and burning bonfires to keep warm.

At first light, groups of them bypassed the official border gate and walked through orchards into Croatia.

Aid agencies are concerned about backlogs of migrants building in the Balkans, battered by autumn winds and rain as temperatures drop before winter.

"The keyword is - cold. It's been freezing, this was our busiest night this week," said ?Astrid Coyne-Jensen of the Danish People's Aid medical team.

Mustafa, wrapped in a blanket, said his group of three families spent the night at the crossing under a piece of discarded tarpaulin as there were not enough tents for everyone.

"I am from Hama in Syria, I have family in Turkey, I will tell them not to ?come as this is not for people, this is for animals," Mustafa said.

Hungary meanwhile said it had no intention of opening any corridor for migrants.

"Hungary has made it abundantly clear...that it does not support any proposal to open corridors on the border sections closed in the south or to provide means of transport for migrants within the Schengen zone," government spokesman Zoltan Kovacs said after a meeting of Croatian, Slovenian, Austrian and Hungarian police chiefs in Vienna.

A police spokesman in the Austrian province of Styria said about 1,500 migrants had been found walking on a road near the Slovenian border and had been transported back to migrant centres.

Almost 6,000 migrants arrived at the port of Pireaus on the Greek mainland on Wednesday on three ferry boats from the islands of Lesbos and Chios, the first point of landfall for many refugees from Syria.

Two boatloads carrying about 140 men, women and children came ashore at RAF Akrotiri on Cyprus, the first time since the crisis began that refugees have landed directly on what is considered British sovereign soil.